At a pet store, there are 30 aquariums. Of the 30, 20 have fresh water with 15 fish in each. The other 10 aquariums have salt water fish with 6 fish each. Which equation could be used to find f, the total number of fish at the pet store?

Becca wants to mix fruit juice and soda to make a punch. she can buy fruit juice for $3 a gallon and soda for $4 a gallon. if she wants to make 28 gallons of punch at a cost of $3.25 a gallon, how many gallons of fruit juice and how many gallons of soda should she buy?